Pneumatic-tire tread



B. DARROW.

PNEUMATIC TIRE TREAD. \XPPLICAUON man MAR, e. 1918.

Patented July 25, 1922 iB'UfR-G-Efifi @ARBOW, QB AKRON, @HIO, AS$IGNOE TO THE GQODYEAR HERE & RUBBER COMPANY, OF IRON, OHIO, A CORPORATION OF OHIO.

PNEUMATIC-TIRE TREAJD.

Application filed March 6, 1918.

To all whom it may concern:

Be it known that I, BURGESS DARROW, a citizen of the United States, residing at Akron, in the county of Summit and State Of Ohio, have invented new and useful Improvements in Pneumatic-Tire Treads, of which the following is a specification.

My present invention relates to pneumatic tires and has for its general object the production of a pneumatic tire wherein the liability of premature destruction through separation of the tread and fabric carcass is efliciently guarded against.

The prevalent practice in the manufacture of a pneumatic tire involves the essential steps of building the fabric carcass; applying the covering strips of rubber, which form the side walls, cushion and tread, (the breaker strip being applied in with the cushion) and curing.

When a pneumatic tire is under load a change in the carcass cross-sectional contour is produced and this changed contour varies constantly in each portion of the tire as bumps, ruts, etc., are encountered and passed over.

One of the results of this change in con tour is a shearing action between the tread strip and fabric carcass. The shearing action of a pneumatic tire under load is most acute in the zones which are located at the outer portions of the-side walls and include the edges of the breaker strip.

This shearing action between'the tread and cushion frequently starts a crack adjacent the edge of the breaker, which gradually results in the failure of the tire through destruction of the union between the tread and carcass. I

It is the function of the cushion strip in a pneumatic tire to guard against disunion or separation between the tread and carcass by taking up, through its elasticity, the shearing action between these elements.

However, while the cushion is usually sufficiently elastic to take up by stretching and without rupture, the shearing action between the fabric and the tread in all other portions of the carcass, it very frequently happens that elasticity of the cushion is not sufficient to take up, in the zones at the outer portions of the side walls, the shearing action resulting from unusual and sudden distortion when the car is overloaded and an unusually severe shock is sustained.

Specification of Letters Patent.

Patented July 25, 1L9%%.

Serial no. 220,753.

When such a shock comes, the cushion is,

by the shearing action, stretched in the zone of the breaker strip edge beyond its limit rupture develops as the tire continues in I service and causes tread separation.

As a means for overcoming the foregoing (lifiiculties and rendering the tire less liable to tread separation, I propose by my present invention to adopt the following expedient:

The painting of the fabric carcass or the cushion in the zone of the breaker strip edge with graphite, soapstone, or the use of any other expedient, which will prevent the cushion and tread from forming a union in this zone during the cure.

Constructing a tire in this manner will permit the tread and carcass to freely move relatively to each other under the shearing action and no rupture can result since no union exists to be broken.

The above and additional objects of a similar nature, which will be hereinafter more specifically treated, may be accomplished by such means as are illustrated in the accompanying drawings, described in the following specification, and then more particularly pointed out'in the claims which are appended hereto and form a part of this application.

/Vith reference to the drawings, wherein there has been illustrated a preferred embodiment of the invention as it is reduced to practice, and throughout the several views of which, similar reference numbers designate corresponding parts:

Fig. 1 is a cross section of a pneumatic tire shown more or less in diagrammatic form and illustrating the manner in which the union between the cushion strip and the carcass is interrupted in the zone comprehending the edge of the breaker strip; and

Fig. 2 is a similar view showing the tire flexed.

Tn illustrating my invention T have shown a tire of a frequently encountered type, known as a straight side cord tire, but I do not wish to be limited to this particular type or otherwise, except by the claims hereto appended, as my invention can be applied to almost any tire of the pneumatic type.

In the drawings the numeral 10 designates the carcass proper, (whichfis formed, of course, of a plurality of cord sheets or layllltl ers) Ll designates the tread cushion; 12 the side walls; 13 the breaker strip, and 141: the tread strip or slab.

After the carcass has been built up in any suitable manner from plies of fabric, a gum strip or thin sheet of rubber is applied to the outer surface, extending from the valley of one bead'to the valley of the other. Suitabl side wall covering strips of rubber applied either in slab form or in small strips, are next put in position and'the tire is then ready to receive the cushionstrip.

Relatively narrow zones upon the surface of the now rubber coated fabric carcass are then painted or otherwise equivalently treated with soapstone or any other material which will prevent the cushion strip from uniting with the carcass when the tire is cured. These zones are located as indicated in the drawing at the outer part of each side wall and in most tires should be situated to comprehend the edge of the breaker strip 18. The cushion strip is then placed centrally on the crown of the tire and then stitched down upon the carcass in the usual manner.

In this connection it should be explained that the width of this zone will vary accord ing to the size of the tire, but the proportions in most instances will be found to make a zone of approximately the dimen sions indicated in Figure 1. After the cushion strip is placed in position over the fab ric carcass thus treated, the tread is applied and the tire then cured in a mold, in a wrap or on an air bag, according to which method of curing is to be followed in finishing the type of tire being built.

In the following claims I use the term tread portion to indicate broadly the cushion, breaker strip and tread slab or strip (which latter I have in some instances designated as the tread proper).

Although I prefer, in view of the results of the experiments thus far completed, to paint or equivalently treat the rubber cover of the fabric carcass, I desire it understood that I also contemplate by my present invention the painting of the cushion or the tread slab.

hat I claim is:

1. A tire of the class described comprising a fabric carcass and a tread portion and having at the outer end of each side wall portion azone wherein the tread portion is free with respect to the carcass and wherein no union exists between the tread and the carcass, the remaining portion of the tread exclusive of the zones mentioned being firmly united to the carcass.

2. A tire of the class described comprising a carcass, a tread, a breaker strip and cushion, and having two parallel zones comprehending the edge of the breaker strip, wherein no union exists between the cushion and the carcass but wherein the cushion and hence the tread are free with respect to the carcass.

3. A tire of the character described comprising a carcass, a cushion, a breaker strip encasing the cushion and a tread encasing the breaker strip and having between the carcass and the cushion at the outer portion of each side Wall an annular zone wherein the carcass and cushion are free with respect to each other, whereby the portions of the tread overlying these zones are free to move with respect to the carcass in response to shearing action superinduced b the imposing of a load upon the tire.

4. In a tire casing, the combination with a tire carcass, of a tread member including a breaker strip and cushion, so mounted on the carcass as to permit of substantially greater yielding of the tread member relative to the carcass along the edges of the breaker strip than elsewhere.

A tire casing embodying a carcass, a tread member and a cushion so mounted on the tire carcass as to permit of substantially greater yielding of the tread member relative to the carcass along the edge portions of the cushion than elsewhere.

6. In a tire casing, the combination with a tire carcass, of a tread member including a breaker strip mounted on the carcass, and non-vulcanizable material interposed between the carcass and the tread member in zones adjacent the edges of the breaker strip.

7. In a tire casing, the combination with a tire carcass and a tread member, of a cushion member interposed between the tire carcass and the tread member with its side portions in unattached engagement with the tire carcass.

8. In a tire casing, the combination with a tire carcass, and a tread member, of an interposed cushion member having portions in sliding engagement with the tire carcass.

9. A tire casing comprising a tire carcass, a tread member including a breaker strip mounted on the carcass, and separated circumferential zones of lubricating material interposed between the carcass and the tread member.

10. A tire casing comprising a tire carcass, a tread member including a breaker strip mounted on the carcass, and circumferential zones of non-vulcanizable lubricating ma terial interposed between the carcass and the tread member adjacent the edges of the breaker strip.

In testimony whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

BURGESS DARROW.

B. J. MCDANEL. 

